The present invention relates to a door pillar for a supporting frame structure of a vehicle body.
European document EP 1 138 581 A2 discloses a door pillar of this type which has an upper section and a lower section. The upper section extends from a vehicle roof as far as a vehicle side edge while the lower section extends from this vehicle side edge in the direction of a vehicle flow. The known door pillar is configured as a single piece in the form of a thin-walled cast steel part. With a body component which is produced from thin-walled cast steel and is not assembled—as previously customary—from a plurality of sheet-metal parts, a considerable saving on weight, for example in the order of magnitude of approximately 25%, can be achieved. Furthermore, wall thickness and shaping can be matched virtually as desired to the particular strength requirements. In particular, wall thicknesses which occur in the case of comparable, conventional body components made of sheet metal can therefore be achieved. Similarly, very complex components can be produced in a single piece, thus omitting the outlay on assembling a plurality of individual sheet-metal components.
The known door pillar is configured as an A-pillar or B-pillar of the supporting frame structure.
It is known from international publication WO 03/031252 A1 to design a door pillar, in particular an A-pillar of a convertible, as a thin-walled cast steel part in such a manner that it has an essentially lattice-like casing which is at least partially filled by a core of metal foam or of metallic hollow spheres and is therefore reinforced.
In the finished motor vehicle, the door pillars of the supporting frame structure have an important safety function, since they help to protect the passenger cell in the event of a crash, in particular if the vehicle rolls over, from a deformation which could put the occupants at risk. Accordingly, the door pillars have to have particularly great strength especially in their upper sections. To date, such strength values cannot be achieved with light metal alloys; consequently, the door pillars have hitherto always been produced from iron or iron alloys, preferably from steel. However, iron materials are comparatively heavy, and so the door pillars have a comparatively high weight. To protect resources, it is, however, desirable for modern motor vehicles to be constructed as lightly as possible, which firstly leads to reduced fuel consumption and secondly to a reduced emission of pollutants.
The present invention is concerned with providing an improved embodiment of a door pillar of the type mentioned which makes it possible to obtain a reduced weight for a vehicle equipped therewith.
The general concept of the invention is to divide the door pillar into at least two components which, although connected fixedly to one another, are produced from different materials. This firstly involves a pillar body which extends at least in the upper section of the door pillar and which is produced from iron or from an iron alloy. This secondly involves a pillar base which extends at least in the lower section of the door pillar and is produced from a light metal alloy. The hybrid construction proposed according to the invention makes it possible to assign different functions to the two components of the door pillar. As a result, the two components can be optimized with regard to the respectively assigned function in terms of selection of material and, in particular, in terms of shaping and method of production. The pillar body produced from iron or iron alloy can be provided straight away with the stability required for the door pillar. In this connection, it has been recognized that the high strength of the door pillar is required only in the upper section, since, in the lower section, other parts of the supporting frame structure additionally contribute to protecting the passenger cell from deformation. From this results the finding that the pillar base manages with lower stability, and so can be produced from a light metal alloy in order to save weight in the lower section of the door pillar. Via the pillar base, the connection of the pillar body to the rest of the supporting frame structure takes place at the same time.
According to an advantageous embodiment, the pillar body extends into the lower section, preferably as far as the vehicle floor. A particularly intensive coupling between pillar base and pillar body can thereby be formed in the lower section. This improves the transmission of the forces occurring during operation or in the event of a crash, thus making it possible to achieve or improve the desired stiffness for the passenger cell.
Of particular interest is an embodiment in which the pillar base is designed as a cast part and is cast onto the pillar body. In such an embodiment, the pillar body can be integrated in the lower section into the pillar base in a particularly simple manner. Simply by the casting-on operation, an adequately fixed connection between pillar body and pillar base can be achieved. By casting the pillar base onto the pillar body additional installation steps for connecting the pillar body to the pillar base can be omitted.
In principle, the pillar body can be produced as desired, for example the pillar body can be configured as a single-part cast part, in particular as a thin-walled cast part. Similarly, it is possible to configure the pillar body as a single-part or multi-part sheet-metal component.
Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures with reference to the drawings.
It goes without saying that the features mentioned above and those which have yet to be explained below can be used not only in the respectively stated combination but also in other combinations or on their own without departing from the scope of the present invention.
A preferred exemplary embodiment of the invention is illustrated in the drawing and is explained in more detail in the description below.